SEABIRDS OFF THE SOUTHWESTERN COAST OF AFRICA

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Abstract
Summerhayes, C. P., Hofmeyr. P. K. & Rioux, R. H. 1974. Seabirds off the southwestern coast of Africa. Ostrich 45: 83–109. The distribution of seabirds off the southwestern coast of Africa was observed during April. May and November, and observed south of Africa in March. Most seabirds off the west coast were concentrated near to the coast or over the edge of the continental shelf. These are sites where forms of upwelling bring water rich in nutrients to the surface of the sea. The most birds were seen in March, April and May, the least in November. Most common over the shelf-edge were, in order of abundance, Blackbrowed Albatross, Cape Hens, Shy Albatross, Yellownosed Albatross, Wilson's Storm Petrels, Cape Gannets, Common/Arctic Terns, and Antarctic Skuas. Seasonal shifts in their ranges and population densities probably reflect the influence of breeding and migration. Comparable concentrations of seabirds were only seen as the cold, nutrient-rich waters of the Subantarctic were approached south of Africa. Here turbulence breaks up the front of the Subtropical Convergence and, in moving large masses of cold water northwards, provides a “corridor” which Southern Ocean species may follow to reach Africa. (Contribution No. 2687 of the Woods Hole Oceanographic Institution).